This project is investigating certain interactions between mechanisms of cardiovascular homeostasis and learning. For example, an increase in baroreceptor stimulation is known to produce inhibition of the reticular formation. We propose to determine whether this inhibition reduces the aversiveness of noxious stimulation in man and also in animals. We also want to see whether such a reduction in aversiveness can serve as a reward for the learning of a skeletal response. If the results of the foregoing experiments are positive, they will suggest that the reduction in aversiveness produced by an increase in baroreceptor stimulation could reinforce the learning and maintenance of essential hypertension. We also want to investigate the possible involvement of learning in the return of heart rate to normal levels after certain interventions that disrupt homeostasis. Finally, we plan to investigate further the unusual ability of human patients with spinal lesions who suffer from postural hypotension to learn to produce large voluntary increases in blood pressure, and plan to develop further the use of rats paralyzed by curariform drugs and trained to make highly specific cardiovascular responses as a possible pure model for analyzing visceral learning.